The capacitance of a capacitor changes with a DC voltage applied to the capacitor, and in an equivalent circuit model of a capacitor disclosed in International Publication No. 2012/090602, changes in the capacitance are taken into consideration by modeling the behavior of the capacitor as a current source in which the amount of current increases or decreases in accordance with the applied DC voltage. That is, in the equivalent circuit model, when a superposed voltage of an alternating-current voltage and a DC bias voltage is applied to a capacitor equivalent circuit section, a reference current generating unit refers to the alternating-current voltage and calculates a reference current. A scaling factor generating unit refers to the DC bias voltage and calculates a scaling factor with the DC bias voltage serving as a variable. A current-source current generating unit refers to the reference current and the scaling factor and calculates a current generated by the current source. The calculated current is generated by the current-source current generating unit and supplied to a basic circuit of the capacitor equivalent circuit section. Therefore, the current flowing to the capacitor equivalent circuit section corresponds to the DC bias characteristics of the actual capacitor and this equivalent circuit model indicates DC bias characteristics that are close to the actual DC bias characteristics as a result of correlating the current with the capacitance of the capacitor.